Abstract
Kazakh horses are a basic breed of Xinjiang horses with strong lactation ability. CircRNAs can be broadly involved in bioregulatory activities through a variety of mechanisms. However, there is relatively little literature on the expression of circRNAs in the milk fat of Ka-zakh horses. Therefore, this study aimed to reveal the potential impact of circRNAs on Kazakh horses’ milk production during their mid-lactation period. To be more specific, the horses were di-vided into the higher-producing (H group) group and the lower-producing group (L group) based on their milk yield, in the middle of lactation. After 300 ml of milk was collected from each horse, RNAs from these milk samples were extracted and purified, and then analyzed with the Illumina NovaSeq 6000 platform. The processed data was compared with the equine genome to select dif-ferentially expressed circRNAs, which are subject to subsequent functional studies. In the two groups, 257 upregulation and 79 downregulation differences in circRNAs were found, and 212 target genes were predicted. The genes (circRNA.12757/CSN1S1, circRNA.9870/ACSL1, circR-NA.9457/LGB1, circRNA.567/VPS13C) enriched by GO and KEGG were located in PPAR signaling pathways, circadian rhythm, insulin signaling pathways, and lactation signaling path-ways.